Researchers from Washington University in St. Louis recently conducted a study, published in the Antimicrobial Agents and Chemotherapyjournal, to determine how chemicals in common household products affect antibiotic medications.

For the assessment, the scientists evaluated mice with bacterial infections and exposed them to triclosan. They treated the infection with antibiotics and tracked their ability to survive over time.

After analyzing the results, they found the antibiotics were less effective in killing bacteria exposed to triclosan. “Triclosan exposure allowed the bacteria to escape death by antibiotics,” the team said in a statement.

“Normally, one in a million cells survive antibiotics, and a functioning immune system can control them,” Petra Levin, professor of biology in Arts & Sciences, explained. “But triclosan was shifting the number of cells. Instead of only one in a million bacteria surviving, one in 10 organisms survived after 20 hours. Now, the immune system is overwhelmed.”

The authors then explored whether the substance could interfere with treating urinary track infections, which is one of the most common infections among women.

They looked at mice with the condition and treated them with the common antibiotic cipro. After the treatment, mice with triclosan exposure still had a large number of bacteria in their urine and stuck to the bladder. On the other hand, mice without exposure had significantly lower bacterial counts.

Why is triclosan preventing antibiotics from working properly?

The scientists believe the ingredient triggers a cell growth inhibitor called ppGpp that make cells less sensitive to antiobiotics.

“During times of stress, ppGpp responds by shutting down the biosynthetic pathways that make the building blocks — DNA, RNA, protein and fat — that ultimately become new cells,” the analysts wrote. “This response helps divert resources away from growth and towards survival.”

This means triclosan in combination with ppGpp curtails biosynthesis, preventing the death of bacterial cells.

When they observed bacteria unable to produce ppGpp, researchers noticed triclosan did not stop antibiotics from working.

While more investigation is needed to confirm their results, the researchers “hope this study will serve as a warning that will help us rethink the importance of antimicrobials in consumer products.”